Optical coordinate input device having light adjusting means located in front of each light receiving means

Abstract

An optical coordinate input device wherein there is no possibility of operation in error or of destruction of a light receiving element and a correct coordinate signal can be produced even if external light of a high intensity acts upon the light receiving element. The device comprises light amount adjusting means of the transmissive type located in front of light receiving elements, and controlling means for controlling the amount of light to be passed through the light amount adjusting means in response to an amount of light incident to the light receiving elements. Thus, if there is the possibility that an output value of the light receiving elements may reach a saturation condition due to external light of a high intensity, the light transmittivity of the light amount adjusting means is lowered to decrease the amount of external light to be received the light receiving elements.

What is claimed is: 
     
       1. In a coordinate input device of the light detection type which includes an optical element train in the form of a framework which is constituted from a large number of light emitting elements and a large number of corresponding light receiving elements both arranged in rows and wherein a position at which light paths defined in front of a display surface of a display device between said light emitting elements and said light receiving elements are interrupted is detected to input coordinates of the position on the display surface of the display device, the improvement which comprises light amount adjusting means of the transmissive type located in front of light receiving portions of said light receiving elements, and controlling means for controlling the amount of light to be passed through said light amount adjusting means in response to an amount of light incident to said light receiving elements. 
     
     
       2. A coordinate input device of the light detection type according to claim 1, wherein said light amount adjusting means includes a liquid crystal plate of the transmissive type. 
     
     
       3. A coordinate input device of the light detection type according to claim 1, wherein said passing light amount adjusting means include PLZT therein. 
     
     
       4. In an optical coordinate input device of the type wherein a large number of light emitting elements are arranged in rows along two sides of directions of the X- and Y-axes while a large number of light receiving elements are arranged in rows along the other two sides of the directions of the X- and Y-axes and in an opposing relationship to said light emitting elements, and said light emitting elements are scanned to be selectively driven one after another to emit light while those of said light receiving elements which oppose to the selectively driven light emitting elements are selected successively whereby coordinate signals are obtained from positions of those of said light receiving elements which do not receive light signals emitted from the selectively driven light emitting elements, the improvement which comprises passing light amount adjusting means located in front of said light receiving elements and including a crystal optical function element having an electro-optical effect or a magneto-optical effect or else an acoustic-optical effect, disturbant light detecting means for detecting the intensity of disturbant light introduced to said light receiving elements, light emitting element driving means for adjusting the amount of light to be emitted from said light emitting elements in response to a detection signal from said disturbant light detecting means, and driving adjusting means for adjusting the light transmittivity of said passing light amount detecting means in response to the detection signal from said disturbant light detecting means. 
     
     
       5. An optical coordinate input device according to claim 3, wherein the intensity of disturbant light is detected by said disturbant light detecting means from one of said light receiving elements which does not oppose to the selectively driven light emitting elements.